//Math对象
//console.log(Math.PI); 
//console.log(Math.E);
//console.log(Math.abs(-3));//绝对值
var num = 3.51;
//console.log(Math.ceil(num));//向上取整，进一法取整
//console.log(Math.floor(num));//向下取整
//console.log(Math.round(num));//四舍五入取整
//console.log(Math.min(5,3));
//console.log(Math.max(20,15,30));
//0 ~ 49
var num = Math.random()*50;
console.log(Math.floor(num));// 0 ~ 49




